Merge pull request volatilityfoundation#1276 from dgmcdona/dgmcdona/w…

…indows-callbacks-validity-check

Windows: Callbacks - fixes bad callback validity check

volatility3/framework/plugins/windows/callbacks.py

@@ -248,8 +248,12 @@ def scan(
             context, layer_name, nt_symbol_table, constraints
         ):
             try:
-                if hasattr(mem_object, "is_valid") and not mem_object.is_valid():
-                    continue
+                if isinstance(mem_object, callbacks._SHUTDOWN_PACKET):
+                    if not mem_object.is_parseable(type_map):
+                        continue
+                elif hasattr(mem_object, "is_valid"):
+                    if not mem_object.is_valid():
+                        continue
 
                 yield cls._process_scanned_callback(mem_object, type_map)
             except exceptions.InvalidAddressException:

volatility3/framework/symbols/windows/extensions/callbacks.py

@@ -1,4 +1,5 @@
 import logging
+from typing import Dict
 
 from volatility3.framework import exceptions, objects
 from volatility3.framework.symbols.windows.extensions import pool
@@ -24,27 +25,54 @@ def is_valid(self) -> bool:
                 and self.Entry.Blink.is_readable()
                 and self.DeviceObject.is_readable()
             ):
+                vollog.debug(
+                    f"Callback obj 0x{self.vol.offset:x} invalid due to unreadable structure members"
+                )
                 return False
 
+        except exceptions.InvalidAddressException:
+            vollog.debug(
+                f"callback obj 0x{self.vol.offset:x} invalid due to invalid address access"
+            )
+            return False
+
+        return True
+
+    def is_parseable(self, type_map: Dict[int, str]) -> bool:
+        """
+        Determines whether or not this `_SHUTDOWN_PACKET` callback can be reliably parsed.
+        Requires a `type_map` that maps NT executive object type indices to string representations.
+        This type map can be acquired via the `handles.Handles.get_type_map` classmethod.
+        """
+        if not self.is_valid():
+            return False
+
+        try:
+
             device = self.DeviceObject
             if not device or not (device.DriverObject.DriverStart % 0x1000 == 0):
                 vollog.debug(
                     f"callback obj 0x{self.vol.offset:x} invalid due to invalid device object"
                 )
                 return False
 
+            header = device.get_object_header()
+            object_type = header.get_object_type(type_map)
+            is_valid = object_type == "Device"
+            if not is_valid:
+                vollog.debug(
+                    f"Callback obj 0x{self.vol.offset:x} invalid due to invalid device type: wanted 'Device', found '{object_type}'"
+                )
+            return is_valid
         except exceptions.InvalidAddressException:
             vollog.debug(
                 f"callback obj 0x{self.vol.offset:x} invalid due to invalid address access"
             )
             return False
-
-        try:
-            header = device.get_object_header()
-            valid = header.NameInfo.Name == "Device"
-            return valid
         except ValueError:
-            vollog.debug(f"Could not get NameInfo for object at 0x{self.vol.offset:x}")
+            vollog.debug(
+                f"Could not get object type for object at 0x{self.vol.offset:x}"
+            )
             return False